1. Field of the Invention
This invention relates to an improved process for the manufacture of acid cheese curd in conventional dairy equipment.
2. Description of the Prior Art
The prior art describes various processes for preparing cheese curd from chemically acidified milk. For example, U.S. Pat. No. 2,982,654 (Hammond, et al.) teaches a cheese curd process wherein an acidogen is added to milk in conjunction with a proteolytic enzyme. This process, which uses acidogen alone without first acidifying the milk, has the disadvantage that it requires too long a period of time to form a curd. U.S. Pat. No. 3,172,767 (Foster, et al.) teaches a process wherein milk is acidified at 4.degree.-5.degree. C and then heated to 29.degree.-82.degree. C, whereupon a proteolytic enzyme is added, to produce a sweet cheese curd. This process does not produce an acid cheese curd and also requires additional equipment for cooling the milk. U.S. Pat. No. 3,406,076 (Little) teaches a process wherein milk must be refrigerated before addition of free acid and requires above normal amounts of proteolytic enzyme.
U.S. Pat. No. 3,620,768 (Corbin) teaches the acidification of cold milk. British Pat. No. 1,247,415 (Battelle) also teaches acidification of cold milk, and moreover states at page 3, lines 3 through 7, that: "It is well known that when milk is acidified at a temperature of about 70.degree. F (21.degree. C) to a pH of about 5.20 or below, it coagulates almost instantly into a granular water coagulation, totally unfit for making cheese." This disclosure is supported, generally, in "Principles of Dairy Chemistry" by Robert Jenness and Stuart Patton (John Wiley and Sons, New York, 1959) at page 310, where it is stated: ". . . sensitivity of casein to coagulation by heat is enormously increased by decreasing the pH a few tenths of a unit below the normal value for milk ."
U.S. Pat. No. 3,882,250 (Loter, et al.) teaches that when milk is acidified at 15.degree.-30.degree. C under vigorous agitation, its pH can be reduced to from about 4.95 to 5.35 without precipitating casein or denaturing the milk so that curd does not form. Acidogen and proteolytic enzyme are then added to the warm acidified milk maintained at these temperatures in a quiescent state for from about 30 minutes to 4 hours to form a curd. The curd is then cut, cooked and used in cheesemaking. In this process, milk temperature remains approximately constant from the time the acidifying agent is added until after the curd is formed so need for complex temperature control and special heating or cooling equipment is eliminated.